A crawler type traveling apparatus drives a vehicle to travel in such a manner that a sprocket wheel drives a crawler chain formed of a large number of track shoes annually pin-linked together. Compared to the case of a wheel-using traveling apparatus, in the case of the crawler type traveling apparatus, the ground contact area is large. As such, the crawler type traveling apparatus is primarily adapted to vehicles for traveling on, for example, unleveled surfaces of the ground, snow covered surfaces of the ground, and soft surfaces of the ground, and in battlefields and civil work sites.
FIG. 1 shows a typical crawler type traveling apparatus. The crawler type traveling apparatus is substantially the same as a crawler type traveling apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2001-225770 (Publication 1). A one-end portion of a track frame 1 is mounted on a vehicle body (not shown) through a pivot shaft 2 such that the one-end portion of the track frame 1 can swing, and an idler tumbler 3 is rotatably axially supported to an end portion on the side of the pivot shaft 2. Bogies 5 including track rollers 6 are mounted to lower portions of the track frame 1. In general, two types exist in regard to the method of mounting track rollers or bogies having track rollers to the track frame: one type is to mount the track rollers by fixing positions thereof and the other type is to mount the track rollers in a vertical direction such that the track rollers swing. In FIG. 1, the crawler type traveling apparatus is shown, which comprises the latter type of bogies including track rollers mounted in the vertical direction such that the track rollers swing. A crawler chain 8 is wound around the idler tumbler 3, the track rollers 6, the sprocket wheel 4, and carrier rollers 7. According to the latter type, the track rollers 6 are movable following a vertical movement of the crawler chain 8, so that even more stable grounding can be accomplished.
FIG. 4 shows an exploded view when the bogie 5 is assembled with respect to the track frame 1, and FIG. 5 is a cross sectional view taken along the line V-V of FIG. 5. FIG. 5 corresponds to, for example, FIG. 2 shown in Japanese Unexamined Patent Application Publication No. 2001-225770 (Patent Publication 1). In basic structures, the crawler type traveling apparatus shown in FIGS. 1, 4 and 5 and component members thereof do not have substantial differences from a crawler type traveling apparatus described below and component members thereof according to an embodiment of the invention.
As shown in FIGS. 4 and 5, the conventional bogie 5 has also a first bogie link 9 and a second bogie link 10. The first bogie link 9 has first and second shaft bearing portions 9a, 9b in a front-rear directional both end portions of the track frame 1. The first and second shaft bearing portions 9a, 9b are forked into pairs of left and right portions, respectively. The first shaft bearing portions 9a, 9a, formed in one end of the first bogie link 9 are rotatably supported on left and right brackets 11, 11 of the track frame 1 via a pin assembly 12, respectively. The second shaft bearing portions 9b, 9b have angularly columnar cavity portions 9b″, 9b″ which are anteroposteriorly communicated, and the second shaft bearing portions 9b, 9b are disposed in positions bent in a vertically lower direction from a horizontal line passing through the first shaft bearing portions 9a, 9a. A pair of left and right second bogie links 10 and 10 independent of one another are inserted into the cavity portions 9b″, 9b″ of the second shaft bearing portions 9b, 9b, respectively, and a central portion thereof is rotatably supported by the second shaft bearing portions 9b, 9b of the first bogie link 9. The second bogie link 10 is formed from a vertically flat, reversed isosceles triangular plate, and a shaft bearing opening 10a is formed in a central portion thereof. The pair of front and rear track rollers 6, 6 are rotatably mounted to both ends of the second bogie links 10, 10.
FIG. 6 is a vertical cross sectional view showing an example of the structure of the conventional pin assembly 12 used in the crawler type traveling apparatus shown in FIG. 5. A pin assembly similar thereto is also shown in U.S. Pat. No. 3,554,588 (Patent Publication 2). FIG. 7 shows an enlarged view of a portion B indicated by an arrow in FIG. 5. Referring to FIG. 4 and in accordance with FIGS. 5 to 7, a conventional configuration of a shaft bearing structure of the first bogie link 9 with respect to the track frame 1 will be described herebelow. The pair of left and right brackets 11, 11 are arranged on lower surfaces of the track frame 1. As shown in FIG. 5, the respective brackets have a pair of left and right, first and second brackets 11a, 11b extending downward vertically in parallel to one another. Pin press-in openings 11c having the center on the same center line are formed in the respective first and second brackets 11a, 11b. Respective portions of the pin assembly 12 are press fitted into the pin press-in openings 11c, 11c of the pair of left and right brackets 11, 11. As shown in FIGS. 5 and 6, the conventional pin assembly 12 includes 14 members in total, which are a pin 13, first to third rings 14 to 16, two spacers 17, four floating seals 18, and four O-rings 19.
In the pin 13, there are formed a lubricating oil filling portion 13a extending along the center line of the pin 13 with one end sealed by a sealing cap and the other end opened; a lubricant outflow hole 13b which linearly radially extends from the lubricating oil filling portion 13a to the outer peripheral surface and opens; and a lubricant passageway 13c that communicates with the opening of the lubricant outflow hole 13b and extends in parallel to the center line of the pin 13 to reach disposition positions of the respective spacers 17.
The first ring 14 and the third ring and 16 are disposed in both end portions of the pin 13, and are irrotatably press fitted into the pin 13. The second ring 15 is interposed between the first and third rings 14, 16, and is externally fitted to the pin 13 rotatably. The first ring 14 is formed of a bottomed ring body, and has a closed portion 14c in a portion opposing an open side end face of the lubricating oil filling portion 13a. Annular recessed grooves 14a, 15a, and 16a for fixedly fitting the floating seals 18 and O-rings 19, respectively, are formed in substantially central portions of respective opposite end faces of the first and second rings 14, 15 and the second and third rings 15, 16. Further, annular spacer fitting grooves 14b, 15b, and 16b, respectively, communicating with the recessed grooves 14a, 15a, and 16a of the first to third rings 14 to 16 and opened on opposite faces and inner peripheral surfaces of the respective first to third rings 14 to 16 are formed in the internal sides of the respective recessed grooves 14a, 15a, and 16a. The respective spacers 17 are slidably fitted in the respective fitting grooves 14b, 15b, and 16b. Inner surfaces of the fitting grooves 14b, 15b, and 16b and the peripheral surfaces of the spacers 17 are used as slide faces.
The respective spacers 17 have rectangular cross sections, and are slidably interposed between the rings 14 to 16 from the viewpoint of difficulty in processing of the pin assembly 12, especially in securing processing accuracy of the respective opposite faces of the first to third rings 14 to 16 and corrective processing during the assembly of the pin assembly 12. Further, in the event that loads in the thrust direction occur when the traveling surface of the vehicle unevenly contacts with the track shoes with vertical irregularity in the right-left direction (right-left direction in FIG. 5) of the track shoes, the spacers 17 are provided to allow the thrust loads to be mutually transferred between either the first ring 14 or the third ring 16 and the second ring 15. As disclosed in Utility Model Registration Publication No. 2560322 (Patent Publication 3), interposing of such spacers has been employed for many years. On the other hand, small gaps are formed between the opposite end faces in the external sides of the recessed grooves 14a, 15a, and 16a provided for fitting the floating seals 18 and the O-rings 19. As a consequence, direct contact does not occur between the end faces of the respective rings 14 to 16, in the conventional pin assembly 12.
In the pin assembly 12 having the construction described above, the second ring 15 is inserted into a pin press-in opening 9a′ of the shaft bearing portion 9a of the first bogie link 9, and first and third rings 14, 16 are press-fixed into a pin closely fitting opening 11a formed in the bracket 11 of the track frame 1. Accordingly, the pin 13 is immobilizably fixed to the bracket 11 of the track frame 1 via the first and the third rings 14, 16, and the first shaft bearing portion 9a of the first bogie link 9 rotates about the pin 13 via the second ring 15. In this event, also the spacers 17 are externally fitted relatively and slidably with respect to the pin 13 and the first to third rings 14 to 16.
On the other hand, the first and third rings 14, 16 of a pin assembly 12 having the same structure as the pin assembly 12 described above are press-fixed onto the inner surface of a pin press-in opening 9′ formed in the second shaft bearing portion 9b of the first bogie link 9. In this event, the second ring 15 of the pin assembly 12 is rotatably inserted together with the spacers 17 into a pin press-in opening 10a′ formed in the shaft bearing opening 10a of the second bogie link 10. Consequently, the first bogie link 9 rotates relative to the track frame 1 via the pin assembly 12, and the second bogie link 10 rotates relative to the first bogie link 9 via another pin assembly 12.
In the meantime, rotation portions of the second ring 15 and the pin 13 and slide contact portions including the spacers 17 between the first to third rings 14 to 16 need to be lubricated with lubricant. However, for the purpose of preventing the lubricant from leaking out and for the purpose of protecting the rotation portions and the slide contact portions from soil particles such as sand and silt, the rotation portions and the slide contact portions are sealed from the outside. FIG. 6 is an enlarged view of peripheral portions of rotation portions and slide contact portions of the second ring 15 and the third ring 16 indicted by the arrow B in FIG. 5. In this case, for sealing purposes, the annular recessed grooves 14a, 15a, and 16a are provided in the central portion of the opposite faces of the respective first to third rings 14 to 16, in which the pair of left and right floating seals 18, 18 are fitted. These floating seals 18, 18 contact with each other under pressure by using the pair of O-rings 19, 19. The floating seals 18, 18 and the O-rings 19, 19 prevent the lubricating oil which is supplied through the lubricant passageway 13c of the pin 13 from flowing to the outside from, for example, rotation portions and slide contact portions, and concurrently prevent soil particles from entering into rotation portions and slide contact portions from the outside.
Patent Publication 1: Japanese Unexamined Patent Application Publication No. 2001-225770
Patent Publication 2: U.S. Pat. No. 3,554,588
Patent Publication 3: Utility Model Registration Publication No. 2560322